Don't show a decimal for zero-precision values in edge cases

Previously, if the value was close to zero, we would show a single
decimal of precision, so that the user could be aware that there
was SOME power draw or feed.

Now, assume that sub-one-watt values are just error, or not worth
showing, and simply use zero-decimal-precision for all such values.

Also, we previously showed a decimal of precision for Percentage
values close to 100%, but now we just round up to 100%.

Contributes to #1328

src/units.cpp

@@ -292,7 +292,7 @@ quantityInfo Units::getDisplayTextWithHysteresis(VenusOS::Enums::Units_Type unit
 		}
 	}
 
-	auto numberOfDigits = [](int value) {
+	auto numberOfDigits = [](int value) -> int {
 		int digits = 0;
 		while (value) {
 			value /= 10;
@@ -306,28 +306,20 @@ quantityInfo Units::getDisplayTextWithHysteresis(VenusOS::Enums::Units_Type unit
 		precision = 0;
 	}
 
-	// If value is between -1 and 1, but is not zero, show one decimal precision regardless of
-	// precision parameter, to avoid showing just '0'.
-	// And if showing percentages, avoid showing '100%' if value is between 99-100.
+	// if the scaled value is large (hundreds or thousands) no need to display all fractional digits after the decimal point.
+	// Possibly clip the precision by 1 or 2 fractional digits for scaled values between 10 and 99,
+	// except for Units_Volt_DC values i.e. don't clip precision for values like 53.35 V DC.
 	precision = precision < 0 ? defaultUnitPrecision(unit) : precision;
-	if (precision < 2 && (scaledValue != 0 && qAbs(scaledValue) < 1)
-			|| (quantity.unit.compare(QStringLiteral("%")) == 0 && scaledValue > 99 && scaledValue < 100)) {
-
-		int vFixed = qRound(scaledValue * 10);
-		scaledValue = (1.0*vFixed) / 10.0;
-		quantity.number = formattingLocale()->toString(scaledValue, 'f', 1);
-	} else {
-		// if the value is large (hundreds or thousands) no need to display decimals after the decimal point
-		int digits = numberOfDigits(scaledValue);
-		if (unit != VenusOS::Enums::Units_Volt_DC || digits > 2) // don't clip precision for values like 53.35 V DC.
-			precision = qMax(0, precision - qMax(0, digits - (precision == 1 ? 2 : 1)));
-
-		const qreal vFixedMultiplier = std::pow(10, precision);
-		int vFixed = qRound(scaledValue * vFixedMultiplier);
-		scaledValue = (1.0*vFixed) / vFixedMultiplier;
-		quantity.number = formattingLocale()->toString(scaledValue, 'f', precision);
+	int digits = numberOfDigits(static_cast<int>(scaledValue));
+	if (unit != VenusOS::Enums::Units_Volt_DC || digits > 2) {
+		precision = qMax(0, precision - qMax(0, digits - (precision == 1 ? 2 : 1)));
 	}
 
+	const qreal vFixedMultiplier = std::pow(10, precision);
+	int vFixed = qRound(scaledValue * vFixedMultiplier);
+	scaledValue = (1.0*vFixed) / vFixedMultiplier;
+	quantity.number = formattingLocale()->toString(scaledValue, 'f', precision);
+
 	return quantity;
 }
 

tests/units/tst_units.qml

@@ -35,12 +35,12 @@ TestCase {
 	function test_percentage() {
 		expect(VenusOS.Units_Percentage, NaN, "--", "%")
 		expect(VenusOS.Units_Percentage, 0, "0", "%")
-		expect(VenusOS.Units_Percentage, 0.4, "0.4", "%")
-		expect(VenusOS.Units_Percentage, 0.55, "0.6", "%")
+		expect(VenusOS.Units_Percentage, 0.4, "0", "%")
+		expect(VenusOS.Units_Percentage, 0.55, "1", "%")
 		expect(VenusOS.Units_Percentage, 14, "14", "%")
 		expect(VenusOS.Units_Percentage, 15.5, "16", "%")
-		expect(VenusOS.Units_Percentage, 99.3, "99.3", "%")
-		expect(VenusOS.Units_Percentage, 99.7, "99.7", "%")
+		expect(VenusOS.Units_Percentage, 99.3, "99", "%")
+		expect(VenusOS.Units_Percentage, 99.7, "100", "%")
 		expect(VenusOS.Units_Percentage, 100, "100", "%")
 	}
 
@@ -60,8 +60,8 @@ TestCase {
 
 			expect(unit, NaN, "--", unitString)
 			expect(unit, 0, "0", unitString)
-			expect(unit, 0.4, "0.4", unitString)
-			expect(unit, 0.55, "0.6", unitString)
+			expect(unit, 0.4, "0", unitString)
+			expect(unit, 0.55, "1", unitString)
 			expect(unit, 14, "14", unitString)
 			expect(unit, 15.5, "16", unitString)
 			expect(unit, 100, "100", unitString)
@@ -152,7 +152,7 @@ TestCase {
 
 		expect(unit, NaN, "--", "kWh")
 		expect(unit, 0, "0", "kWh")
-		expect(unit, 0.0005, "0.5", "Wh")
+		expect(unit, 0.0005, "1", "Wh") // precision of three for kWh means precision of zero for Wh.
 		expect(unit, 0.005, "5", "Wh")
 		expect(unit, 0.3458, "346", "Wh")
 		expect(unit, 0.5, "500", "Wh")